Processing photographic elements containing developing agent



April 4, 1967 P T W ET AL 3,312,550

PROCESSING PHOTOGRAPHIC ELEMENTS CONTAINING DEVELOPING AGENT Filed Sept.4, 1962 2 Sheets-Sheet l EXPIOSURE I SILVER HALIDE EMULSIONEa-PYRAZOLIDQNE, ALKALI STAGE I r I I SUPPORT HEAT I3 I --sII.vER IMAGEawm awyi STAGE 2 II Io SILVER I-IALIDE EMULSION WITH EXPOSURE DIAMETEROFAVERAGE GRAIN L5 MICRONS OR Lass l4 3-PYRAZOLIDONE AND ALKALI STAGE Isuppom STABLE HIGH COVERINGI POWER 5 SILVER NEGATIVE IMAGE STAGE 2 I6STABLE LOW COVERING POWER SILVER BACKGQOUND SUPPORT SILVER HALIDEEMULSION WITH DIAMETER OF AVERAGE STAGE 1 GRAIN 0.5 T0 1.5 MICRONS 3-PYRAZOLIDONE ALKALIQAND 1-PHENYL-5-MERcAPToTEmAzcILE SUPPORT I HOT MOISTAIR STABLE LOW covsrama DOWER SILVER BACK GROUND $TAGE 2 STABLE HIGHCOVERING woweR SILVER POSITIVE IMAGE SUPPORT PAUL. H- STEWART GEORGE E.FALLESEN JOHN W. REEVES JR.

JNVENTORS BY ATTORNEY & AGENT April 4, 1967 H, STEWART ET AL 3,312,550

PROCESSING PHOTOGRAPHIC ELEMENTS CONTAINING DEVELOPING AGENT Filed Sept.4, 1962 2 Sheets-Sheet 2 PAUL H. STEWART GEORGE E. FALLESEN JOHN w.QEEVES JR.

INVENTORS BY %7LWMZ 73 CM Q ATTORNEY & AGENT United States Patent3,312,550 PROCESSING PHOTOGRAPHIC ELEMENTS CON- TAINING DEVELOPING AGENTPaul H. Stewart, George E. Fallesen, and John W. Reeves,

Jr., Rochester, N.Y., assignors to Eastman Kodak Company, Rochester,N.Y., a corporation of New Jersey Filed Sept. 4, 1962, Ser. No. 221,03143 Claims. (Cl. 9663) This invention relates to photographic elementscontaining silver halide developing agents, methods for processing thesame, and more particularly to such photo graphic elements adapted toprocessing with heat.

This application is a continuation-impart of Stewart, Fallesen andReeves US. patent application Ser. No. 134,014, filed Aug. 5, 1961, nowabandoned, which is a continuation-in-part of Stewart, Fallesen andReeves U.S. Ser. No. 805,582, filed April 10, 1959, now abandoned.

A common procedure in the protographic art involves exposure of a silverhalide emulsion layer to a subject followed by development of theresultant latent image with an alkaline solution of a silver halidedeveloping agent such as hydroquinone to produce a silver image in theregions of the latent image. Fixing and washing steps customarilyfollow.

It has also been proposed to incorporate the silver halide developingagent into the sensitive element, for example, into the silver halideemulsion layer, in which case development of the exposed emulsion can beinitiated mereby by application of an alkaline solution. It is alsoknown that in case both the developing agent and the alkali required toactivate the developing agent are present in the sensitive element,development of the emulsion can be initiated by merely applying water.

We have discovered that certain photographic elements comprising alatent image in a silver halide emulsion layer, contiguous silver halidedeveloping agent and alkali, may be processed without use of aqueous orother liquid solutions by merely heating the element preferably in thepresence of water vapor.

One object of the invention is to provide the sensitive elements adaptedparticularly to the dry development process of the invention, that is,development with heat in the absence of a liquid developing solution.

Another object of the invention is to provide the methods and apparatusparticularly adapted to use in the dry development of the sensitivephotographic elements of the invention.

Another object of the invention is to provide an element which whenprocessed in the single step process of the invention, that is,processing in the absence of liquid processing solutions will producestable silver images.

Still other objects will become evident from the following specificationand claims.

Sensitive elements of our invention include the combination of at leastone silver halide emulsion layer, a 3-pyrazolidone silver halidedeveloping agent and an alkaline substance effective to acceleratedevelopment of a latent image in the silver halide emulsion in thepresence of the developing agent. The element may further include asaccharide, particularly a nonreducing oligosaccharide, such as sucroseor raflin-ose; and preferably, as an auxiliary developing agent, anascorbic acid or polyhydric phenol silver halide developing agent.Additional ingredients which may be present in the sensitive element aredeveloper preservatives such as sulfite and fog reducers such asbenzotriazoles. The mentioned alkaline substance, developing agent andsuccharide are disposed integral with the sensitive element andcontiguous to the silver halide, that is, either directly in the silverhalide emulsion or in an effectively adjacent colloid layer or layers.Thus, the primary developing agent, the 3- pyrazolidone compound, may bepresent in the silver halide emulsion and the auxiliary developingagent, alkali and saccharide in an adjacent colloid layer. Similarly,both developing agent, alkali and saccharide may be present in a layerunderlying or overlying the emulsion on a support. Useful combinationsof developer ingredients, include a 3-pyrazolidone developing agent asthe sole developing agent, in combination with a saccharide; a3-pyrazolidone in combination with an ascorbic acid and, if desired, asaccharide, and the combination of a 3- pyrazolidone developing agent, apolyhydric phenol developing agent, and if desired, a saccharide.

Included among the preferred sensitive elements of our invention arethose which have light-sensitive emulsions with silver halide grainshaving diameters of 1.5 microns or less. Usually the silver halides inthese emulsions are predominantly silver bromide. These emulsions arepreferably free of sulfur and gold sensitizers. Such emulsions whencoated without the alkali and without the developing agent atapproximately 1500 square feet per mole of silver halide, on a papersupport and exposed through a step wedge varying in density from 4.0 to0.03 to a high intensity light source and then processed in a developerof the following composition:

1-phenyl-3-pyrazolidone 5.0 Sodium sulfite 6.0 Sodium metaborate,octahydrate 90.0 Ascorbic acid 27.0 Potassium bromide 2.0 Sodiumthiosulfate, pentahydrate 2.0

Water to make 2 liters.

for 16 minutes at 30 C. gives a minimum reflex density less than 0.35and a maximum density of a least 0.20 greater than the minimum density.In one embodiment, our preferred elements are used to make stablenegative reproductions of an original and in another embodiment they areused to make stable positive reproductions of an original by our onestep process.

The process of invention embody the steps of recording latent images inthe silver halide emulsions in the presence of the developing agents andother ingredients mentioned above, followed by heating the emulsionsutficiently to develop silver images therein. In a representativeprocedure, a sensitive element of the invention containing a smallamount of moisture is exposed to a subject, then subjected to heat bypassing over a heated roller at temperatures of the order of 50 to 200C. and speeds of the order of 10 to 200 feet per minute. As a result, asilver image is formed. In another procedure, an exposed sensitiveelement containing the mentioned ingredients is passed through a heatedchamber so designed that moisture rising from heating of the sensitiveelement is confined to a relatively small space. In another procedure,

the exposed sensitive elements of the invention are processed bysubjecting them to the action of hot air containing moisture in therange from a moderate amount to the amount required to saturate the air.Steam can be used to advantage. Our preferred light-sensitive elementsupon exposure to a light image are developed directly to stable silverimages simply by treatment in an atmosphere at least saturated withwater vapor at a temperature .tiguous layer.

'a silver image in area 13 as shown in stage 2.

a; above 50 C. The silver images obtained by heat development of theother elements of our invention may be stabilized after processing so asto prevent their deterioration during storage.

The 3-pyrazolidone developing agents are essential components of thesensitive elements and are unique in their activity in the drydevelopment process of the invention as compared to other silver halidedeveloping agents. That is, it will be shown in the examples below thatwhen one sensitive element containing both l-phenyl- 3-pyrazolidone andascorbic acid and a second element containing bothmonomethyl-p-aminophenol and hydroquinone are exposed and heated undervarious conditions, only. a faint silver image is obtained in the latterelement. On the other hand,.the 3-pyrazolidone-ascorbic acid system ofthe invention yielded a high density silver image under the sameconditions of treatment.

Moreover, it is important that in addition to alkali a substantialamount of the 3-pyrazolidone developing agent be present'in the silverhalide emulsion or in a con- For example, an emulsion containing noalkali and no more than about 2 grams of 3-pyrazolidone compound permole of silver halide, upon exposure and heating yield no visible silverimage. When about to 50 grams of 3-pyrazolidone compound per mole ofsilver halide is present, only a faint visible image is obtained uponheating in the absence of alkali. However, in the presence of strongalkali, about to grams of 3-pyrazolidone per mole of silver halide issufiicient to produce a high density silver image upon heating thelatent image. When an auxiliary developing agent such as ascorbic acidor hydroquinone is present in addition to the .S-pyrazolidone compoundand a saccharide, as little as five grams of 3-pyrazolidone developingagent per mole of silver halide is sufficient. Of course, the3-pyrazolidone-containing emulsions free of alkali may be developed withalkaline solutions, if desired containing additional developing agentsas Elon and hydroquinone;

Accompanying drawings show in greatly enlarged crosssectional views, theappearance of a representative sensitive element of the invention atdifferent stages of processing and means for heat processing theelement.

In the. element of FIG. 1 of the drawings, layer 10 represents a supportsuch as paper, synthetic resin or cellulose ester carrying a layer 11 ofdeveloper ingredients including a 3-pyrazolidone developing agent andalkali and if desired, other ingredients such as the auxiliarydeveloping agent and a saccharide. Layer 12 is an emulsion layer such asa gelatino-silver halide emulsion layer which may contain any of thementioned developer ingredients in addition to silver halide. As shownin the drawings, the process of the invention includes the exposure ofthe sensitive element to a subject to record a latent image in thesilver halide in area 13 of layer 12. Thereafter, the element is heatedsufliciently to develop In this process, it will be observed that whenthe sensitive element is heated, a visible silver image is obtainedalmost instantaneously. This result is facilitated by the use in theemulsion layer of silver halides which have short development inductionperiods, such as a fine grain silver bromide emulsion. Emulsions havinglonger induction periods are useful but require longer application ofheat to effect their development in the processes of the invention.

In the element of FIG. 2 of the drawings, layer 10 represents a supportcarrying layer 14 comprising silver halide emulsion (predominantlysilver bromide) with grains having an average diameter of 1.5 microns orless, a B-pyrazolidone and an alkali. As shown in the drawings, theprocess of the invention includes exposure of the sensitive element to asubject to record a latent image in the silver halide in area 15 oflayer 14. Thereafter,

the element is treated with air at a temperature above 50 C. and atleast 95% saturated with water vapor as shown in stage 2. This processresults in the formation of a stable negative, comprising high coveringpower silver image 15 against a low covering power silver background 16.

In the element of FIG. 3 of the drawings, layer 10 is a support carryinglayer 17 comprising silver halide emulsion (predominantly silverbromide) with a diameter of average grain from 0.5 to 1.5 microns, a3-pyrazolidone, alkali, and l-phenyl-S-mercaptotetrazole. The element isexposed to an image in stage 1 and processed to a stable positive imagein stage 2 by treatment with air at a temperature above 50 C. and atleast saturated with water vapor. The positive image is formedconsisting of stable high covering power silver in area 19 and stablelow covering power silver is formed in area 18.

In FIG. 4 is illustrated one means for carrying out the heating step ofthe invention so as to accelerate development of the exposedphotographic element and to prevent undue drying of the sheet duringheating. A sensitive element 20 having a structure such as shown instage 1 of FIG. 1 and having a support 10 of medium thickness such as apaper stock of 16 to 20 lbs. per thousand square feet, is passed aroundroller 21, thence over the heated roller 23, with the paper support 10in contact with the roller 23, thence between rollers 24 and 25. Thelatter roller may be a roller driven at a suitable speed and pressedinto contact with sheet 20 in order to draw the sheet off the supplyroll, not shown, and advance it around rollers 21, 23 and 24. Byarranging the rollers and advancing the paper in a manner such as shownin FIG. 4, it is possible to trap moist, warm air in the space 22 abovethe sheet which humid atmosphere facilitates development of the paper. Asimilar effect can be obtained by partially enclosing roller 23 in amanner such that the sheet is heated with its emulsion surface in,contact with warm, moist atmosphere of limited volume. 1 However, it isusually not necessary to apply moisture to the sensitive element duringthe heating operation and a small amount of moisture such as 510%obtainable by drying and handling the sensitive paper at about 3050% RH,is satisfactory. In a typical installation, roller 23 may be about 4inches in diameter and heated to a temperature of about 200 C. Since thepaper can be advanced at the rate of about 30 feet per minute in thisapparatus and still obtain adequate development of the image, the paperdoes not dry out to any great extent under these conditions. Under otherconditions, it may be desirable to supply moisture to the sheet duringthe heating step in order to obtain reproductions of optimum quality.

The pyrazolidone silver halide developing agents, such as thosedescribed below, are useful in our invention. The 3-pyrazolidonecompounds having the following genera Formula I are particularly usefulin. the sensitive elements a in which the various R groups representsubstituents such as hydrogen, alkyl, acyl, heterocyclic or aryl groups,for example, R can be alkyl of from 1 to 12 carbon atoms, benzothiazolylor an aryl group of the benzene or naphthalene series, substituted ornot. R R R and R can be hydrogen atoms or alkyl groups of from 1 to 12carbon atoms or aryl groups such as phenyl and naphthyl, substituted ornot. Typical substituents are lower alkyl groups, including haloalkyl,pyridiniumor picolinium-N- alkyl halide, e.g., pyridinium-N-methy-lchloride, benzyl, phenyl, 4-methylphenyl, 4-methoxyphenyl, carboxylicacid acyl as acetyl, benzoyl, nitrobenzoyl and haloacyl,

.g., chloroacetyl, phenoxy and alkylphenoxy.

The 3-pyrazolidone developing agents of our invention which are used toadvantage particularly with gold and sulfur sensitized silver halideemulsions are represented by the following formulas:

II R5 wherein R and R each represent a hydrogen atom or an alkyl grouphaving from about 1 to 12 carbon atoms such as methyl, ethyl, propyl,isopropyl, butyl, secondary butyl, tertiary butyl, amyl, isoamyl,tertiary amyl, hexyl, etc.; and R represents a hydrogen atom, an alkylgroup or a carboxylic acid acyl group such as methyl, ethyl, propyl,isopropyl, butyl, amyl, tertiary amyl, hexyl, chloromethyl, bromomethyl,chloroethyl, chloropropyl, pyridinium- N-methyl chloride,pyridinium-N-ethyl chloride, benzyl, etc.; or an aryl group such asphenyl, 4-methylphenyl, 4-methoxyphenyl, acetyl, dichloroacetyl,propionyl, 4-nitrobenzoyl, aryloxy such as 2,4-di-tert.amylphenoxy, andR and R represent alkyl or aryl groups such as above.

The compounds above which contain the acyl substituents R and R areparticularly useful because they are developing agent precursors and arenot active developing agents until the acyl group has been split ofi? inthe presence of alkali. Accordingly, these acyl derivatives in whichactive positions of the pyrazolidone nucleus are blocked, are veryuseful in the emulsions especially in the higher concentrations of theorder of 100 to 200 gms. per mole of silver halide. When alkali is alsopresent in the sensitive element it may be desirable to segregate itfrom the acyl derivative to prevent premature release of the active formof the developing agent. The 4-alkyl and 4,4-dialkyl substitutedcompounds behave similarly.

The compounds are not to be confused with 5-pyrazolidones such asl-phenyl-S-pyrazolidone.

The following compounds are representative of the 3-pyrazolidonecompounds useful for the purposes of our invention.

(1 1-phenyl-3-pyrazolidone (2) 1-p-tolyl-3-pyrazolidone (3)1-phenyl-4-methyl-3-pyrazolidone (4) 1-phenyl-2-benzoyl-3-pyrazolidone(5) 1-p-chlorophenyl-3-pyrazolidone (6) 1-phenyl-5-phenyl-3-pyrazolidone(7) 1-m-tolyl-3-pyrazolidone (8) l-phenyl-S-methyl-3-pyrazolidone v (23)1-p-diphenyl-4,4-dimethyl-3-pyrazolidone (38) 2-(pyridiniumacetyl)-1-phenyl-3-pyrazolidone chloride (39) 2-(pyridiniumacetyl)-4-methyl-l-phenyl-3- pyrazolidone chloride (40) 2-(pyridiniumacetyl)-4,4-dimethyl-1-phenyl-3- pyrazolidone chloride (41)3-acetoxy-1-phenyl-2-pyrazoline in equilibrium with (42)3-acetoxy-4-methyl-1-phenyl-2-pyrazoline in equilibrium with enolacetate of 4-methyl-1-phenyl-3-pyrazolidone Compounds 1 to 12 can beprepared by the methods described in British Patents 679,677 and679,678. Compounds 13 to 23 and 26 above are representative of 4,4-dialkyl-B-pyrazolidone compounds useful in this invention and thesecompounds are described in Allen et al. US. Patent 2,772,282, Nov. 27,1956.

The w-hydroXyalkylphenyl-3-pyrazolidones in which the alkyl grouppreferably contains from 1 to 4 carbon atoms, for example, compounds 18to 24 above, are described in the Allen et al. invention and in theReynolds and Tinker U.S. Patent 2,743,279, Apr. 24, 1956.

Compound 33 was prepared as follows: 1-phenyl-3- pyrazolidone (16.2 g.,0.1 mole) and acetic anhydride (1S ml.) were heated to reflux and onedrop of concentrated sulphuric acid was added. The solution was refluxedfor five hours and then evaporated under reduced pressure. The residuewas refluxed for one-half hour with water ml.), cooled and neutralizedwith concentrated ammonium hydroxide. The mixture was extracted withethyl acetate. The solvent was removed and the residue distilled, B.P.11931 14.93 g., 70.5% yield, M.P. 72- 4 from ethyl acetate-lightpetroleum (B.P. ,5565). The infrared spectrum of this material showedtwo carbonyl absorptions at 5.63 and 5.8 indicating that the materialwas the N-acetyl derivative.

Compound 34 was prepared as follows: 1-phenyl-3- pyrazolidone (5.0 g.,0.038 mole) was suspended in a solution of benzene (100 ml.) andpyridine (2.5 g., 0.30 mole) and chloroacetyl chloride (3.5 g., 0.031mole) Was slowly added while stirring. The reaction mixture was thenheated to reflux for 2 hours. After cooling, the solution was washedwith water and the solvent removed to leave an oil which wasrecrystallized from ethyl acetate-light petroleum (B.P. 5565), M.P.9798, 3.5

g., 47.7% yield.

The infrared spectrum of this material showed two carbonyl absorptionsat 5.62,u indicating that the material was the N-acyl derivative.

Compound 35 was prepared as follows: 1-phenyl-4- methyl-3-pyrazolidone(17.6 g., 0.1 mole) and acetic anhydride ml.) were heated to reflux andone drop of concentrated sulphuric acid was added. Refluxing wascontinued for four hours. The excess acetic acid and acetic anhydridewere removed under reduced pressure and the residue was refluxed for 30minutes with 10 ml. water. The solution was cooled and neutralized withammonium hydroxide and extracted with ether. The ether was removed fromthe extract and the residue distilled B.P. 112 12.26 g., 56% yield. Theinfrared spectrum of this material showed two carbonyl absorptions at5.75,u., 5.85 indicating that the material was the N-acetyl derivative.Compounds 36 and 37 are prepared similarly.

Compound 38 was prepared as follows:2-chloroacetyl-1-phenyl-3-pyrazolidone (6 g.) prepared as above, wasdissolved in absolute ethanol (10 ml.) and ethyl acetate (25, ml.). Theresulting solution was heated to reflux and an excess of pyridine added.The crystalline product separated on cooling and was collected and wasrecrystallized from absolute ethanol-ethyl acetate or ether. Thisproduct has a M.P. of 213-14".

Compound 39 was prepared by the same procedure just above but using2-chloroacetyl-4-methyl-l-phenyl- 3-pyrazolidone. The2-chloroacetyl-4-methyl-l-phenyl- 3-pyrazolidone was prepared by theprocedure used for compound 34 but starting with4-methyl-1-phenyl-3-pyrazolidone in place of 1 phenyl 3 pyrazolidone.The product compound 39, has a M.P. 22931.

Compound 40 was prepared by the procedure for compound 38 but using2-chloroacetyl-4,4-dimethyl-1- phenyl-3-pyrazolidone which was preparedfrom 4,4-dimethyl-1-phenyl-3-pyrazolidone by the same method used forcompound 34. Compound 40 had a M.P. 26870.

Compound 41 was prepared as follows: A suspension of1-phenyl-3-pyr-azolidone (40 g.) in benzene (300 ml.) was heated on asteam cone. Ketene was passed in until all the material had dissolvedand then for an additional one-half hour. The solvent was then removedunder reduced pressure, to leave an oil which solidified on cooling. Thematerial was recrystallized from benzene-light petroleum (B.P. 65-75) toyield a white crystalline solid M.P. 84-5 29.15 g., 58% yield.

The infrared absorption spectrum of this material showed a singlecarbonyl absorption at 5.72u, indicating that the material was theO-acetyl derivative.

Compound 42 was prepared as follows: 1-phenyl-4- methyl-3-pyrazolidone(25.0 g., 0.142 mole) was dissolved in refluxing benzene (300 ml.) andketene (0.11

mole per hour) was passed in for one and one-half hours. The solvent wasthen removed under reduced pressure to leave an oil which wascrystallized from ethyl acetatelight petroleum (B.P. 55-65"), M.P.62.4", 11.52 g., 37.25% yield.

The infrared spectrum of this material showed a single carbonylabsorption at 5.6a, indicating that the material was the O-acetylderivative.

Our light-sensitive elements are designed for development withconventional aqueous developer solutions or an alkaline aqueous solutioncontaining no developing agent, which may be applied to the exposedemulsion in a conventional manner.

While the processes of the invention can be carried out with sensitiveelements containing a 3-pyrazolidone silver halide developing agent asthe sole developing agent, in a preferred embodiment of the invention, a3-pyrazolidone developing agent is used in combination with ascorbicacid silver halide developing agent, such as dand l-ascorbic acids,d-arabo ascorbic acid, iminogluco-ascorbic acid and other ascorbic acidshaving the formulas shown in James et al. US. Patent 2,688,549, grant-edSept. 7, 1954. Alternately, the 3-pyrazolidone developing agents areemployed in combination with a polyhydric phenol silver halidedeveloping agent such as hydroquinone, catechol, 4-phenylcatechol orpyrogallol. As mentioned previously, when a 3-pyrazolidone is used incombination with these auxiliary developing agents, appreciably less ofthe 3-pyrazolidone compound is required in the sensitive element tomaintain high development activity and thus produce the silver imageswith a minimum of heating of the exposed emulsion layer. An added eflectof 4-phenylcatechol in combination with a 3-pyrazolidone developingagent is that the permanence of the print obtained upon heat developmentis improved. That is, the residual silver halides show less tendency toprint-out upon exposure to light than in the case when the3-pyrazolidones are used as the developing agent in the sensitiveelement.

The saccha-rideshave previously been employed in a sensitive element inorder to improve the stability of the emulsion upon againg for extendedperiods of time. However, in the present invention one unexpected effectof the saccharides, especially of the non-reducing oligosaccharides suchas sucrose and raffinose, results from their ability to enhance thedevelopment activity of the 3-pyrazolidone developing agents, alone orin combination with the auxiliary developing agents. Thus, in thepresence of a s-aocharide, much less of the 3-pyrazolidone compound needbe used in the sensitive elements to maintain high development activity.Representative saccharides which may be used are: fructose, glucose,inulin, melecitose, pectin, raffinose, starch, sucrose and trehalose.The non-reducing oligosaccharides such as sucrose and raffinose areespecially useful.

Non-reducing has a meaning herein usually applied to saecharides andmeans that the compounds are members of the class of saccharides whichdo not reduce alkaline solutions of salts of metals such as coppersalts,-as present in Fehlings solution, as compared to reducing sugarslike fructose.

Latent images in the preferred light-sensitive elements of our inventionhaving emulsions with silver halide grains with diameters of 1.5 micronsor less and containing predominantly silver bromide and which have thespecific sensitometric characteristics described before :in terms of Dand the differences between D, and D are developed directly to stableimages by treatment in an atmosphere at least saturated with water vaporat a temperature above 50 C. The silver halide grains in these elementswhen processed as described are substantially all converted to silver.The image formed is com prised of high covering power silver with a lowcovering power silver background. These images are stable as formedsince there is substantially no residual silver halide. These preferredelements give direct stable negative images. It is believed that theexposed areas are chemically developed to form the black high coveringpower filamentary silver while the unexposed areas are solutionphysically developed to form hexagonal crystals of silver, approximately50 to 200 millimicrons in diameter. Where the hexagonal silver crystalsrange in size from approximately 80 to 100 millimicrons, the backgroundcolor appears greenish when viewed by reflected light. Covering powerdecreases and image tone becomes progressively lighter and browner assilver particles approach a diameter of approximately 150 to 200millimicrons. We have found that stable direct positive images areproduced by relatively coarser grained emulsions, that is when the graindiameter is from 0.5 to 1.5 microns and heterocyclic mercaptan compoundsor aromatic mercaptan compounds, such as mercaptotetnazoles,meroaptobenzoxazoles, mercaptobenzothiazoles, toluene thiols, and thelike, are added to the silver halide emulsion, and the exposed elementsare processed in air saturated with mois ture at 99 C. for one toseveral minutes. The meroaptotetrazoles, e.g.,1-phenyl-5-mercaptotetrazole are preferred. By adding sodium thiosulfate(usually 50l00 g. per mole of silver halide) in addition to thel-phenyl-S- mercaptotetrazole, a stable positive print is obtained inapproximately 30 seconds with some increase in D occurring.

In our preferred elements which are developed directly to stable prints,the rate of print stabilization may be increased in many ways known toincrease the rate of solution physical development, e.g., silver halidesolvent (such as sodium thiosulfate, etc.), solvent transfer nuclei anddevelopment accelerators as coating addenda. Adding solventtransfer-type nuclei, such as yellow colloidal silver, zinc sulfide orreduced silver formed by solution physically developing a portion of thesilver halide grains prior to or during coating, increased the printstabilization rate approximately three times. Development accelerators(e.g., u-picolinium-B-phenylethyl bromide or dodecylpyridinium-p-toluene sulfonate) also increase print stabilization rateby approximately three times.

Latent images in the other light-sensitive elements of our inventiongive photographic reproductions (as a direct result of heating of thealkaline emulsions containing a 3-pyrazolidone developing agent)comprising silver images and residual unreduced silver halide which iscapable of being subsequently exposed and developed by heat in the samemanner. That is, after forming one image in the emulsion layer by meansof the exposure and heat development steps, the residual emulsion may bere-exposed and redeveloped with heat any number of times until theunexposed and undeveloped emulsion has been exhausted. Accordingly, thesensitive elements can be used for posting items at various times andheat developing emulsion at a convenient time after the entry has beenmade. Since the prints obtained in the process will usually contain someresidual silver halide and developing agent, they should not besubjected to light and moisture for any prolonged period of time,otherwise appreciable density will appear in the background regions. Ifit is desired to prevent formation of this background density, this maybe accomplished by treating the prints with a desensitizing agent, anantifoggant, acid or other compound inhibiting development of the silverhalide. For example, this may be accomplished by dusting the compoundonto the surface of the print and steaming the print to cause thecompound to penetrate the emulsion. The following compounds arerepresenative of those suitable for this purpose:6-chloro-4-nitrobenzotriazole, 5-chlorobenzotriazole,B-methylbenzothiazolium methylsulfate, a mixture of6-chloro-4-nitrobenzotriazole and sulfamic acid. It has also been foundthat mercaptans (e.g., thiosalicylic a'cid,1-phenyl-5-mercaptotetrazole) present either in the emulsion layer, orcontiguous to the emulsion layer, can serve as post-exposurestabilizers. Such compounds do not materially improve the stability ofthe unexposed product,

10 however, they do serve as post-exposure stabilizers since afterexposure and heat processing of the sensitive elements under theconditions described, the mercaptans appear to react with the residualsilver halide to form a much less light-sensitive silver salt than theoriginal silver halide.

Useful amounts of the various ingredients in the sensitive elements canbe ascertained from the following examples although optimum quantitiesshould be ascertained under the particular conditions in use. However,3- pyrazolidone compound such as l-phenyl-3-pyrazolidone may be used inamounts in excess of about 20 grams per mole of silver halide and whenin combination with an auxiliary developing agent such as ascorbic acidor hydroquinone, an amount in excess of about 5 grams per mole of silverhalide should be used. Quantities of the 3-pyrazolidones in excess ofabout 50 grams per mole of silver halide may be difficult to disperse inmany silver halide emulsions. However, somewhat larger amounts of fromabout 50-to 200 grams per mole of silver halide can be used. Thesaccharides may be used in combination with the pyrazolidones in amountsranging from about 30 to 1000 grams per mole of silver halide. If toolarge a quantity is used, crystallization occurs or the emulsion tendsto be tacky, depending upon the particular saccharide used. Theauxiliary developing agents such as the ascorbic acids may be used incombination with the 3-pyrazolidones in amounts of the order of about30100 grams per mole of silver halide and the polyhydric phenoldevelopers such as hydroquinone in the range .of about 15 to 75 gramsper mole of silver halide. However, at the higher levels ofconcentration, the latter developing agent tends to produce morebackground stain in the prints than desired.

The following examples will serve to illustrate .our invention.

Example 1 Sample 1.-48 grams of a 20% gelatin solution were added to 500cc. of the following solution.

Water to make 1.0 liter.

The mixture was then coated upon a baryta-coated photographic paper baseat a coverage of about 8 grams of solution per square foot. The alkalinelayer was then overcoated with a gelatino-silver bromoiodide emulsion(94.5 mole percent silver bromide, 5.5 mole percent of silver iodide)containing 50 grams of I-phenyl-B-pyrazolidone and 320 grams .of sucroseper mole of silver at a coverage of approximately 475 square feet permole of silver.

Sample 2.A coating similar to that of Sample 1 was prepared exceptomitting the sucrose from the emulsion. Samples 1 and 2 were processedfresh by exposure under a step tablet and passing the samples over ametal surface heated at 200 C. at a rate of 20 feet per minute in anapparatus similar to that described on page 39, line 13. Sample 1 had animage having a maximum density of 1.65 and Sample 2, a maximum densityof 1.60. When Samples 1 and 2 were incubated eight days at F., and 35%relative humidity, the maximum density obtainable in Sample 1 was 1.60and in Sample 2, only 0.76. When Sample 1 was aged six months and Sample2 for three months, at 75 F. and 50% relative humidity, the respectivemaximum densities obtained were 1.54 (Sample 1) 0.52 (Sample 2).

The effect of sucrose in stabilizing the developing agent in the coatedelement is thus apparent from these data.

It is interesting to note that the sensitive elements of the inventioncontaining silver halide in combination with a 3-pyrazolidone developingagent and alkali are developable with heat under a wide range ofconditions, i.e., as mentioned above, when the emulsions are conditionedat 35% relative humidity, the emulsions develop readily upon heating.Even when the sensitive elements are conditioned at 17% or lowerrelative humidity, the emulsions develop readily upon heating regardlessof the fact that a comparatively small amount of moisture is present.

Processors similar to that described on page 39, line 13, were also usedin the following Examples 2, 3, 4, 5, 6, 8, 9 and 11.

Example 2 A coating was made on a paper support in the manner of Example1, except that 48 grams of 20% gelatin solution were added to 500 cc. ofthe following composition:

Grams l-phenyl-3-pyrazolidone 2.5 Sodium sulfite, anhydrous 45.0Hydroquinone 12.0 Potassium bromide 1.0 Sodium metaborate, octahydrate45.0 S-methyl-benzotriazole .02

Water to make 1 liter.

This was coated on .a paper support at 8 grams of solution per squarefoot followed by the bromoiodide emulsion free of developing agentcoated at 475 square feet per mole of silver. Upon exposing the coatingand heat developing at 200 C. a maximum density of 1.60 was obtained inthe fully exposed areas.

Example 3 A gelatino bromoiodide emulsion (94.5% silver bromide, 5.5%silver iodide) was coated on a paper base at 475 square feet per mole ofsilver. This emulsion layer was then overcoated with a compositionconsisting of 48 'grams of 20% gelatin solution added to 500 cc. of thefollowing developer solution:

Grams l-phenyl-3-pyrazolidone 2.5 Sodium sulfite, anhydrous 45 .0Ascorbic acid 13.5 Potassium bromide 1.0 Sodium metaborate, octahydrate45.0 S-methylbenzotriazole 0.2

Water to make 1 liter.

An exposed sample of the coating when developed as described at 200 C.gave a maximum density of 1.40.

Example 4 The inability of the 3-pyrazolidone developing agents todevelop a useful image in silver halide in the absence of alkali evenwhen the developing agent is present in high concentrations isillustrated by this example.

Three gelatin solutions each containing 1-phenyl-3-pyrazolidone werecoated on a paper base and each coating then overcoated with abromoiodide emulsion at 475 square feet per mole of silver, so as toobtain coverages of 2, 10 and 50 grams of 1-phenyl-3-pyrazolidone permole of silver. When these coatings were exposed and heat developed at200 C. only the coating containing 50 grams of l-phenyl-3-pyrazolidoneper mole of silver showed any image at all and this was extremely faint.At the 2 and 10 gram levels no image was visible.

Similar coatings prepared by adding 2, 10 and 50 grams of1-phenyl-3-pyrazolidone per mole of silver to the bromoiodide emulsionyielded images of very low density and then even only at the highestconcentration (50 grams of pyrazolidone per mole of silver).

1 2 Example 5 48 grams of 20% gelatin solution were added to 500 cc. ofthe following composition:

Grams 1-phenyl-4,4-dimethyl-3-pyrazolidone 2.5 Sodium sulfite, anhydrous45.0 Ascorbic acid 13.5 Potassium bromide 1.0 Sodium metaborate,octahydrate 45.0 S-methylbenzotriazole .02

Water to make 1 liter.

The solution was coated on a paper base and the resulting coating thenovercoated with a bromoiodide emulsion at 475 square feet per mole ofsilver. Upon heat development at 200 C. of the exposed emulsion, amaximum density of 1.4 was obtained.

Example 6 A dispersion was prepared of a mixture of 46 grams of4-phenyl-catechol, 69 grams of di-n-butylphthalate, 460 grams of 10%gelatin solution and 23 cc. of 15% saponin solution. This was added toan unhardened gelatin silver bromoiodide emulsion containing one mole ofsilver halide and the emulsion coated on a paper support which hadpreviously been coated with a gelatin layer containing sodium carbonate.Upon heat development of the coating by passing through a chamber heatedat 200 C. and at a rate of 10 feet per minute for about one secondimagewise tanning development occurred and washing in water removedunexposed areas. A maximum density of 1.4 was obtained in the fullyexposed regions and 0.06 in the unexposed regions.

Example 7 A silver bromoiodide emulsion was prepared containing amixture of monomethyl-p-aminophenol sulfate and hydroquinone developingagents by diluting 48 grams of a 20% gelatin solution with 208 cc. ofwater and adding to 300 cc. of the following developer composition:

Water cc 500 Monomethyl-p-aminophenol sulfate "grams" 4.5 Sodiumsulfite, anhydrous do 45.0 Hydroquinone do 12.0 Sodium carbonatemonohydrate do 80.0 Potassium bromide do 2.0

Water to make 1 liter.

This composition was then coated upon a photographic paper base at acoverage of 8 grams of solution per square foot. .The layer was thenovercoated with a gelatino-siler bromoiodide emulsion (94.5% silverbromoiodide, 5.5 mole percent silver iodide) at a coverage of 475 squarefeet per mole of silver. A comparable emulsion was prepared by thefollowing procedure: 96 grams of 20% gelatin solution were added to oneliter of a 1- phenyl-3-pyrazolidone-ascorbic acid developer solution,given in Example 3 above, and the mixture coated on a baryta-coatedpaper base at a coverage of about 9 grams per square foot. This layerwas then overcoated with the above emulsion at 475 square feet per moleof silver halide. When the papers were exposed and heat processed bypassing them over a surface heated at 200 C., at speed of 10 and 12 feetper minute, the highest maximum density obtainable in the first paperwas 0.30 whereas the 1-phenyl-3-pyrazolidone-ascorbic acid paper of theinvention yielded densities as high as 1.20 under the same conditions oftreatment.

Example 8 Coatings were prepared as described in Example 2 except thatthe hydroquinone in the developer composition was replaced by 13.5 gramsper liter of d-araboascorbic acid or 15.5 grams per liter ofiminoglucoascorbic acid. When the samples were heat processed at 200 C.passing 13 over the heated surface at 20 feet per minute, they yieldedmaximum densities of 1.65 and 1.66 respectively.

Example 9 50 grams of sucrose in 48 grams of 20% gelatin solution wereadded to 500 cc. of the following developer composition and coated on aphotographic paper base at 9.0 grams of solution per square foot:

Grams 1-phenyl-3-pyrazolidone 2.5 Sodium sulfite, anhydrous 45.0 Sodiumascorbate 15.0 Potassium bromide 1.0 Sodium metaborate, octahydrate 45.0S-methylbenzotriazole 0.02

Water to make 1.0 liter.

The developer layer was then overcoated with a gelatinosilverbromoiodide emulsion containing approximately 94.5 mole percent AgBr and5.5 mole percent AgI at a coverage of approximately one mole of silverper 475 square feet. A similar coating containing no sucrose wasprepared as a control. Additional coatings were prepared in the samemanner except replacing the sucrose by the following:

Grams Fructose 25 Raflinose 50 Inulin 25 Melezitose 25 Trehalose 50 Thecoatings were exposed and heat developed at 200 C. with the resultsshown in the following table:

max. Sample Fresh 8 days 1 16 days 1 3 mo.

Control.. 1. 60 0.3 Sucrose 1. 62 1. 60 Fructos 1.60 1. 08 Raffinose- 1.60 1. 62 InulirL 1. 60 1. 58 Melezitose. 1. 70 l. 56 Trehalose 1. 601.68

Example 10 In a less preferred process a direct positive photographicpaper comprising a fogged silver chloride emulsion was immersed brieflyin a solution of 100 cc. water, 100 cc. methanol, 2 g.l-phenyl-3-pyrazolidone and 10% triethanolamine followed by drying. Anexposed silver halide emulsion layer was placed in contact with thepaper containing the alkaline developer composition and heated betweenmetal surfaces at 180 F. for about one second, resulting in thedevelopment of a silver image in the exposed emulsion layer.

Example 11 A fine grain gelatin-o silver bromoiodide emulsion (94.5 molepercent AgBr and 5.5 mole percent AgI) containing 320 g. sucrose, 162 g.ascorbic acid, 90 g. l-phenyl- 3-pyrazolidone, 36 g. Na SO 540 g. sodiummetaborate, octahydrate, 12 g. KBr, 178 g. lphenyl mercaptotetrazole and40 g. NaOH per mole silver halide was coated on single weight paper at acoverage of approximately 1300 sq. ft./ mole silver handle. A strip ofthe coating exposed and processed by passing over a heated surface asdescribed in Example 1 at 150 C. at a paper speed of about 7 ft. perminute gave a stable print having a D of 0.96 and 0.03 density in theunexposed areas. Similar coatings in which the l-phenyl-S-mercaptotetraz-ole was replaced with either mercaptobenzoxazole, orp-toluene t'niol also produce stable prints.

When the developer is added directly to the silver halide emulsionlayer, it is sometimes advantageous to add the developer solution to theemulsion just prior to coating. This can be done by using a proceduresimilar to that described in Collins et al. U.S. Patent 2,912,343.

Example 12 A negative speed sulfur and gold salt sensitized bromoiodideemulsion preparation was divided into aliquot portions and solutions ofthe following developing agents added just before coating. Each of thepreparations was coated on a light-weight paper in an amount equivalentto 200 mg. Ag per ft. and dried. After sensitometric exposure, thepapers were developed 25 seconds at 32 C. in a developer having thefollowing composition:

Grams p-Methylaminophenol sulfate 2.2 Hydroquinone 8.8 Sodium sulfite,anhydrous 72.0 Sodium carbonate, anhydrous 48.0 Potassium bromide 4.0

Water to 1 liter.

then fixed, washed, and dried. Relative speeds were measured atreflection densities of 0.1 above fog.

The following Table I lists the relative speeds, fogs, and reflection Dvalues for the control emulsion and each of the emulsions containing3-pyrazolid0ne developing agents.

TABLE I Developing Agent Incorporated Into Rela- Reflec- Emulsion 20g./mole silver tive Fog tion Speed Dim;

Control 0. 02 1.16 l-phenyl-3-py1azolidone 200 0. 06 1. 21l-phenyl-Z-chloroaeetyl-3-pyrazolidone 152 0. 03 1. 181-phenyl-2-ch1oroacetyl-4-methyl-3-pyrazolidone 0. 03 1. 201-phenyl2-acetyl-3-pyraz0lidone 100 O. 04 1. 201-phenyl-2-acetyl-4-methyl-3-pyrazolidone.. 100 0. 02 1.18 Enol acetateof l-phenyl-3-pyrazolidone. 166 0. 02 1. 20 Enol acetate of1-phenyl-4-methyl-3-pyrazolidone 159 0. 02 1. 2O4-methyl-l-phenyl-3-pyrazolidone 0. 03 1; 20

Another identical set of coatings containing the 3-pyrazolidones ofTable I were incubated 8 days at 120 F.

and 35% RH. with the result that the coatings containing the3-pyrazolidone derivatives substituted by acyl and acetoxy radicals inthe 2- and 3-positions and alkyl in the 4-position of the nucleus werefound to be most stable.

This example illustrated the development properties of the 2- and 3-acyland 4-alkyl substituted 3-pyrazolidones, which as mentioned areeflicacious for use in emulsions, particularly those sulfur and goldsensitized, since the acyl derivatives do not become effective asdeveloping agents until the acyl radical is split off in the presence ofalkali. The 4-alkyl derivatives behave similarly. Alkali can be added tothese sensitive elements preferably in a layer effectively separate fromthe acyl derivative, and the elements subjected to heat development bythe method described in Example 1.

Example I 3 A high speed sulfur and gold salt sensitized silver Ibromoiodide emulsion was prepared and coated in the normal fashion.Portions of this emulsion, containing to modulate the infrared exposure.

1. 5 the 3-pyrazolidones listed in the Table II were coated on a papersupport. Samples of each coating were exposed on an intensity scalesensitometer, processed for 25 seconds in the developer used. in Example12 at 32 C., fixed,

16 Example 14 A gelatino silver bromoiodide emulsion consisting ofsilver halide grains having a diameter of approximately washed and driedwith the following results. 5 50 millimicrons containing 320 g. ofsucrose was coated TABLE 11 Amount of De- Developing Agent Incorporatedveloping Relative Fog Din.

Into Emulsion Agent, Speed gJmole silver Control 100 0. 02 1.13l-phenyl-3-pyrazolidone 20 166 0. 02 1. 194-methyl-l-phenyl-3-pyrazolidone 13. 3 138 0. 02 l. 18 20. 166 0. 02 1.17 H1 26. 7 121 O. 4 irnethyl-lhenyl-3- azolidone 13.3 1 8 0.

p pyr 20.0 152 0. 04 1.18 1- -(2-hydroxyethylphenyDl-3- pyrazolidoue 13.3 132 0- 04 l- 5 20. 0 132 0.05 1. 18 26. 7 152 0.06 1. 18

When samples of these emulsions were incubated for 8 days at 120 F. and35% R.H., it was noted that the emulsions containing the 4-methyl and4,4-dimethyl substituted compounds were substantially more stable.Additional 3-pyrazolidone derivatives have general Formulas II and 111above, and particularly compounds 32 to 41, may be used in the emulsionssensitized with sulfur compounds and the gold salts such as mentionedbelow, to obtain improved stability arising out of this particularemulsion sensitizing in combination with the 3-pyraz-olidonesunsubstituted in the 5 -position but substituted in the 2-, 3- and4-positions of the pyrazolidone nucleus.

A single element paper readily developable with heat may be prepared bycoating a silver halide emulsion on a suitable paper support and thenovercoating the silver halide emulsion layer with a solution of 400 ml.methanol, 40 g. of Aerosol OT (dioctyl ester of sulfosccinic acid), and10 g. of 1 phenyl-3-pyrazolidone followed by drying. This paper, afterexposure, is readily developable by applying to it a uniformly heatedsurface (250-3 00 F.) for several seconds. A further paper readilydevelopable with heat may be made by impregnating an emulsion with asolution of 12.5 g. l-phenyl-3-pyrazolidone, 1.0 g. thiosalicylic acid,12.5 cc. phenylhydrazine and 1000 cc. methyl alcohol.

The processes of the invention are further applicable to use withsensitive elements comprising .a support such as paper, upon the supporta gelatin layer of alkaline developer ingredients such as used inExample 1, Sample 1, and over that alkaline layer the gelatino-silverhalide-3- pyrazolidone-sucrose layer to which has been added a quantityof wax such as paraffin and a dye suitable for carrying out thetherm-ographic exposure step described below. The sensitive element isexposed to a subject then subjected to heat under conditions such asdescribed in Example 1 in order to develop a silver image in the exposedareas. Thereafter the element is placed with the emulsion side incontact with a thin sheet of absorbent paper and exposed to infraredradiations, with the result that the wax in the region of the silverimage melts and transfers with the dye to the absorbent sheet yielding adye image of the subject thereon. In this process the amount of silverhalide in the emulsion layer may be extremely small since only a faintsilver image is needed Thus the mentioned emulsion of Example 1 coatedover the alkaline layer can contain as little as 1 mole of silver halideper 5000 or more square feet of coating surface.

The following examples will serve to illusrate the preferred elements ofour invention and their processing with heated air at least 95%saturated with water vapor to produce stable prints.

on single weight paper stock at a coverage of approximately 1600 ft./mole of silver as silver halide. The emulsion layer was then overcoatedwith a solution consisting of 48 g. of a 20% gelatin solution and 500ml. of a 1-phenyl-3-pyrazolidone, ascorbic acid developer having thecomposition:

1-phenyl-3-pyrazolidone 2.5 Sodium sulfite 45.0 Ascorbic acid 13.5Potassium bromide 1.0 Sodium metaborate, octahydrate 45.0 Water to make1 liter.

at a coverage of approximately 9.0 g. per ft. A strip of the coating,when imagewise exposed and subjected to air saturated with moisture at95 C. for 15 seconds, gave a legible print having a dense black image ona brown background of relatively low density. The print was dry to thetouch. Exposing to 50 ft.-c. illumination for one hour under highrelative humidity conditions (90 percent R.H. at F.) did not alter theappearance of the print. A strip of the coating was exposed by means ofan intensity scale sensitometer, processed as described in this example,and the resulting image density measured with a reflection densitometer.The log exposure at a density of 0.8 was 2.50, Dmax, 1.33 and D 0.60.

Example 15 A gelatino silver bIOtl'IlOlOdldC emulsion consisting ofsilver halide grains having a diameter of approximately 50 millimicronscontaining the following materials per Sodium metaborate, octahydrate540.0 Potassium bromide 12.0

Was coated on a single weight paper at a coverage of approximately 1500ftF/m'ole of silver halide. A strip of the coating when imagewiseexposed and processed as described in Example 14 gave a legible printhaving a black image on a light brown background. The log exposure at adensity of 0.8 was 2.52, D 1.48 and D like 0.40. Another element likethis was made but with a faster gelatino silver bromoidide emulsioncontaining silver halide grains with diameters of approximately 250millimicrons. This was exposed, processed and its image densitiesmeasured as described. The log exposure at a den y f 0.8 was 0.39,D,,,,,, 1.30 and D,,,,,, 0.38.

A gelatino silver bromoiodide emulsion consisting of silver halidegrains having a diameter of approximately 1.5 microns containing thefollowing materials per mole of silver halide:

Sucrose 640.0 Ascorbic acid 162.0 1-pheny1-3-pyrazolidone 30.0 Sodiumsulfite 36.0

Sodium metaborate, octahydrate 540.0 Potassium bromide 12.01-phenyl-5-mercaptotetrazole 10.0

was coated on single-weight paper stock at a coverage of approximately1600 ft. per mole of silver halide and then air dried. A similar coatingwas made in which the l-phenyl-S-mercaptotetrazole was omitted. Animagewise exposed strip of the coating containing the l-phenyl-S-mercaptotetrazole, when subjected to air saturated with moisture at 99C. for 2 minutes, gave a legible direct positive print with a D of 0.71and D of 1.21. The coating which contained no 1 phenyl 5mercaptotetrazole when exposed and processed in a similar manner for 15seconds gave a legibile negative print with a D of 0.52 and a D of 1.06.Exposing both prints to 30 ft.-c. illumination for one hour under highrelative humidity conditions (90% R.H., 75 F.) did not alter theappearance of the print.

Another element like this was made but in which 100 g. of sodiumthiosulfate per mole of silver halide was also included along with the1-phenyl-5-mercaptotetrazole. An irnagewise exposed strip of thiselement when subjected to air saturated with moisture at 99 C. for 30seconds gave a legible stable positive print with a D of 1.64 and D of0.76. Exposure of the print to actinic light under elevated temperatureand humidity as described above did not alter the prints appearance.

The elements of Examples 14, 15 and 16 have been processed to stabilizedprints by treatment with air saturated with water vapor at temperaturesas low as 50 C. The following table lists the temperatures andprocessing times used to advantage.

TABLE III Approximate processing time, minutes Water vapor saturated airtemperature, C.:

The type elements illustrated by Examples 14, 15 and 16 are processed toadvantage by passing the light exposed element through hot moist airwhich is at least about 95% saturated with water vapor for the requiredtime. The water vapor may be supplied in any convenient way, for exampleas steam, or water vapor fi'om the element itself if contained in aheated enclosed processor of the type described by Stewart et al. inPhotographic Science and Engineering, vol. 5, No. 2, Part 1 of 2 parts,March-April 1961, page 113. We have found that such a processoroperating with a paper travel speed of approximately 15 feet per minutewill process our preferred elements to advantage.

Our stable prints can be copied with the immediate elements or withoffice copy materials that are used conventionally.

The alkaline materials present in the sensitive elements together withthe developing agents include inorganic alkalies such as sodiummetaborate, octahydrate, sodium hydroxide and sodium carbonate. Organicalkaline materials such as quaternary ammonium bases and salts can beused although the inorganic alkalies which do not yield volatile basesupon heating, are preferred.

The elements and processes of the invention have been described withrespect to ordinary developing emulsions. If desired, sensitive elementscontaining direct reversal emulsions and the 3-pyrazolidone compoundsmay be used in a similar manner.

The photographic emulsions used in practicing our invention are of thedeveloping-out type.

The emulsions can be chemically sensitized by any of the acceptedprocedures. The emulsions can be digested with naturally active gelatin,or sulfur compounds can be added such as those described in SheppardU.S. Patent 1,574,944, Sheppard and Punnett U.S. Patent 1,623,499, andSheppard and Brigham U.S. Patent 2,410,689.

The emulsions can also. be treated with salts of the noble metals suchas ruthenium, rhodium, palladium, iridium, and platinum. Representativecompounds are ammonium chloropalladate, potassium chloroplatinate, andsodium chloropalladite which are used for sensitizing in amounts belowthat which produces any substantial fog inhibition, as described inSmith and Trivelli U.S. Patent 2,448,060, and as antifoggants in higheramounts, as described in Trivelli and Smith U.S. Patents 2,566,245 and2,566,263.

The emulsions can also be chemically sensitized with gold salts asdescribed in Waller, Collins and Dodd U.S. Patent 2,399,083 orstabilized with gold salts as described in Damschroder U.S. Patent2,597,856 and Yutzy and Leermakers U.S. Patent 2,597,915. Suitablecompounds are potassium chloroaurite, potassium aurithiocyanate,potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazolemethochloride.

The emulsions can also be chemically sensitized with reducing agentssuch as stannous salts (Carroll U.S. Patent 2,487,850), polyamines, suchas diethylene triamine (Lowe and Jones U.S. Patent 2,518,698),polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925), orbis(fi-aminoethyl)sulfide and its Water-soluble salts (Lowe and JonesU.S. Patent 2,251,926).

The emulsions can also be optically sensitized with cyanine andmerocyanine dyes, such as those described in Brooker U.S. Patent1,846,301, 1,846,302, and 1,942,854; White U.S. Patent 1,990,507;Brooker and White U.S. Patents 2,112,140, 2,165,338, 2,493,747, and2,739,964; Brooker and Keyes U.S. Patent 2,493,748; Sprague U.S. Patents2,503,776 and 2,519,001; Heseltine and Brooker U.S. Patent 2,666,761;Heseltine U.S. Patent 2,734,900; Van Lare U.S. Patent 2,739,149; andKodak Limited British Patent 450,958. 1

The emulsions can also be stabilized with the mercury compounds ofAllen, Byers, and Murray U.S. Patent 2,728,663; Carroll and Murray U.S.Patent 2,728,664, and Leubner and Murray U.S. Patent 2,728,665; thetriazoles of Heimbach and Kelly U.S. Patent 2,444,608; the azaindenes ofHeimbach and Kelly U.S. Patents 2,444,605 and 2,444,606; Heimbach U.S.Patents 2,444,607 and 2,450,397; Heimbach and Clark U.S. Patent2,444,609; Allen and Reynolds U.S. Patents 2,713,541 and 2,743,181;Carroll and Beach U.S. Patent 2,716,062; Allen and Beilfuss U.S. Patent2,735,769; Reynolds and Sagal U.S. Patent 2,756,147; Allen and SaguraU.S. Patent 2,772,164, and those disclosed by Birr in the Z. wiss. Phot.47, 2 (1952); the quaternary benzothiazolium compounds of Brooker andStand U.S. Patent 2,131,038; and the zinc and cadmium salts of JonesU.S. Patent 2,839,405 and the'isothiourea derivatives of the Herz andKalenda U.S. applicaber 15, 1960, of Milton and Murray; an ester of anethylene bis-glycolic acid such as ethylene bis(methyl glycolate) (asdescribed in U.S. Patent 2,904,434 of Milton); bis- (ethoxy diethyleneglycol) succinate as described in U.S. Patent 2,940,854 of Gray or apolymeric hydrosol as results from the emulsion polymerization of amixture of an amide of an acid of the acrylic acid series, and acrylicacid ester and a styrene-type compound as described in U.S.

;Patent 2,852,386 of Tong. The plasticizer may be added to the emulsionbefore or after the addition of a sensitizing dye, if used.

The emulsion may be hardened with any suitable hardener for gelatin suchas formaldehyde; a halogen-substituted aliphatic acid such as mucobromicacid as described in U.S. Patent 2,080,019 of White; a compound having aplurality of acid anhydride groups such as 7,8-diphenylbicyclo(2,2,2) 7octene 2,3,5,6-tetracarboxylic dianhydride, or a dicarboxylic or adisulfonic acid chloride such as terephthaloyl chloride ornaphthalene-1,5-disulfonyl chloride as described in U.S. Patents2,725,294 and 2,725,- 295 of Allen and Carroll; a cyclic 1,2-diketonesuch as cycl-opentane-1,2-dione as described in U.S. Patent 2,725,- 305of Allen and Byers; a bisester of methanesulfonic acid such. as1,2-di-(methanesulfonoxy)ethane as described in U.S. Patent 2,726,162 ofAllen and Laakso; -1,3-dihydroxyrnethylbenzimidazole-2-one as describedin U.S. Patent 2,732,316 of July, Knott and Pollak; a dialde- Jeffrey'set al. U.S. Ser. Nos. 822,444, 822,445, and 822,-

446, all filed June 24, 1959.

The emulsions may have been supplied with a coating aid such as saponin;a lauryl or oleyl monoether of polyethylene glycol as described in U.S.Patent 2,831,766 of Knox and Davis; a salt of a sulfated and alkylatedpolyethylene glycol ether as described in U.S. Patent 2,719,087 "of Knoxand Davis; an acylated alkyl taurine such as the sodium salt ofN-oleoyl-N-methyl taurine as described in U.S. Patent 2,739,891 of Knox,Twardokus, and-Davis; the reaction product of a dianhydrideoftetracarboxybutane with an alcohol or an aliphatic amine con- .tainingfrom 8 to 18 carbon atoms which is treated with a base, for example, thesodium salt of the monoester of tetracarboxybutane as described in U.S.Patent 2,843,487 of Knox, Stenberg and Wilson; a water-solublemaleopimarate or a mixture of a water-soluble maleopimarate and asubstituted glutamate salt as described in U.S. Patent 2,823,123 of Knoxand Fowler; an alkali 'metal salt of a substituted amino acid such asdisodium N-(carbo-p-tert. octylphenoxypentaethoxy)glutamate as describedin U.S. application Serial No. 600,679 of Knox and Wilson; or asulfo-succinamate such as tetrasodium'N-(1,2-dicarboxyethyl)-N-octadecyl sulfosuccinamate or N-laury1disodium sulfosuccinamate as described in U.S.

Patent 2,992,108 of Knox and Stenberg.

In the preparation of the silver halide dispersions employed forpreparing silver halide emulsions there may be employed as thedispersing agent for the silver halide in its preparation, gelatin orsome other colloidal material such as colloidal albumin, a cellulosederivative, or a synthetic resin, for instance, a polyvinyl compound.Some colloids which may be used are polyvinyl alcohol or a hydrolyzedpolyvinyl acetate as described in U.S. Patent 2,286,215 of Lowe; a farhydrolyzed cellulose ester such as cellulose acetate hydrolyzed to anacetyl content of 1926% as described in U.S. Patent 2,327,808 of Loweand Clark, a water-soluble ethanolamine cellulose acetate as describedin US. Patent 2,322,085 of Yutzy; a polyacrylamide having a combinedacrylamide content of 30-60% 'and a specific viscosity of 0.251.5 or animidized polyacrylamide of like acrylamide content and viscosity asdescribed in U.S. Patent 2,541,474 of Lowe, .Minsk and Kenyon; zein asdescribed in U.S. Patent 2,563,791 of Lowe; a vinyl alcohol polymercontaining urethane carboxylic acid groups'of the type described in U.S.Patent 2,768,154 of Unruh and Smith, or containing cyano-acetyl groupssuch as the vinyl alcoholvinyl cyanoacetate copolymer as described inU.S. Patent 2,808,331 of Unruh, Smith and Priest; or a polymericmaterial which results from polymerizing a protein or a saturatedacylated protein with a monomer having a vinyl group as described inU.S. Patent 2,852,382 of I11- ingsworth, Dann and Gates.

If desired, compatible mixture of two or more of these colloids may beemployed for dispersing the silver halide in its preparation.Combinations of these antifoggants, sensitizers, hardeners, etc., may beused.

It may be advantageous, in some instances, to use as the photographicemulsion support a paper base having a thin metal foil, e.g. aluminum,laminated to it. The foil appears to cut down loss of heat and moisturefrom the region of development.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be eifected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

We claim:

1. A light-sensitive, unexposed photographic element comprising asupport having thereon a silver halide emulsion layer and contiguous tothe said silver halide, an alkaline material and at least about 5g./mole of silver halide of a 3-pyrazolidone selected from those havingthe formulas:

.wherein R represents a member selected from the class consisting ofhydrogen, and anacyl' group; R1 represents a substituent selected fromthe class consisting of an alkyl group having from 1 to 12'carbon atoms,a benzothiazolyl group and an aryl group; and R R R and R each representa substituent selected from the class consisting of hydrogen, an alkylgroup havingfrom 1 to 12 carbon atoms and an aryl group; R represents agroup selected from the class consisting of an alkyl group having from 1to 12 carbon atoms, and an aryl group; and R represents a group selectedfrom the class consisting of an alkyl group having from 1 to 12 carbonatoms and an aryl group; and an auxiliary developing agent selected fromthe class consisting of a polyhydric phenol and an ascorbic aciddeveloping agent and when none of said auxiliary developing agent ispresent, at least about 15 g./mole of silver halide of said3-pyrazolidone' silver halide developing agent, said element containinga small amount of moisture that is suflic'ient to develop a latent imagein said silver halide to a silver image upon heat ing to a temperatureabove about 50 C,

21 2. A photographic element of claim 1 containing contiguous to thesilver halide a saccharide.

3. A photographic element of claim 1 containing contiguous to the silverhalide a non-reducing oligossaccharide.

4. A photographic element of claim 1 in which the 3- pyrazolidone isl-phenyl-3-pyrazolidone.

5. A photographic element of claim 1 containing at least about 15g./mole of silver halide of an auxiliary developing agent.

6. A photographic element of claim 1 containing contiguous to the silverhalide a saccharide and at least about 30 g./mole of silver halide ofascorbic acid.

7. A photographic element of claim 1 containing contiguous to the silverhalide a non-reducing oligosaccharide and at least about 30 g./mole ofsilver halide of ascorbic acid.

8. A photographic element of claim '1 containing contiguous to the saidsilver halide sucrose and at least 30 gm/mole of silver halide ofascorbic acid.

9. A photographic element of claim 1 containing contiguous to the silverhalide a saccharide and at least about 15 g./mole of silver halide of apolyhydric phenol.

10. A photographic element of claim 1 containing contiguous to thesilver halide a non-reducing oligosaccharide and at least about 15g./mole of silver halide of hydroquinone.

11. A photographic element of claim 1 containing contiguous to thesilver halide, sucrose and at least 15 g./ mole of silver halide ofhydroquinone,

12. A photographic element of claim 1 wherein the alkaline material anddeveloping agent are present in a layer between the emulsion layer andthe support.

13. A photographic element of claim 1 wherein the alkaline material anddeveloping agent are present in a layer overlying the emulsion layer.

14. A photographic element of claim 1 wherein the alkaline material ispresent in a layer between the emulsion layer and support, and thedeveloping agent is present in the emulsion layer.

15. A photographic element of claim 1 wherein the alkaline material anddeveloping agent are present in the emulsion layer.

16. A photographic element of claim 1 containing contiguous to thesilver halide at least about 30 g./mole of silver halide of anon-reducing oligosaccharide.

17. A photographic element of claim 1 containing a mercaptan.

18. A photographic element of claim 1 in which the silver halideemulsion is a sulfur and gold sensitized silver halide emulsion.

19. A photographic element of claim 1 in which the silver halideemulsion is a sulfur and gold sensitized silver halide emulsion and the3-pyrazolidone developing agent is selected from the class consisting of1-phenyl-4- methyl-3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazoli-,done, 1 phenyl 2 acetyl 3 pyrazolidone, 3-acetoxyl-phenyl-Z-pyrazoline,the enol acetate of 1-phenyl-3- pyrazolidone,3-acetoxy-4-methyl-1-phenyl-2-pyrazoline and the enol acetate of4-methyl-1-phenyl-3-pyrazolidone.

20. A photographic element of claim 1 wherein the alkali is sodiummetaborate, octahydrate.

21. A photographic element of claim 1 having contiguous to the silverhalide a non-reducing oligosaccharide and in which the alkali is sodiummetaborate octahydrate.

22. A photographic element of, claim 1 containing a mercaptotetrazoleand in which the silver halide emulsion has silver halide grains havingan average diameter in the range from approximately 0.5 to 1.5 micronsand the silver halide is predominately silver bromide.

23. A photographic element of claim 1 containing a mercaptotetrazole andan alkali metal thiosulfate and in which the silver halide grains havean average diameter in the range from approximately 0.5 to 1.5 micronsand the silver halide is predominately silver bromide.

24. A photographic element of claim 1 that contains ascorbic acid and inwhich the silver halide emulsion has silver halide grains having anaverage diameter of less than approximately 1.5 microns and the silverhalide is predominately silver bromide.

25. A photographic element of claim 1 that contains ascorbic acid andsodium thiosulfate and in which the silver halide emulsion has silverhalide grains having an average diameter of less than approximately 1.5microns and the silver halide is predominately silver bromide.

26. A photographic element of claim 1 that contains an organic cyclicmercaptan compound and in which the silver halide emulsion has silverhalide grains having an average diameter in the range from approximately0.5 to 1.5 microns and in which the silver halide is predominatelysilver bromide.

27. A photographic element of claim 1 in which the silver halideemulsion has silver halide grains having an average diameter of lessthan approximately 1.5 microns and the silver halide is predominatelysilver bromide.

28. A light-sensitive, unexposed photographic element comprising asupport having thereon a silver halide emulsion layer and contiguous tothe said silver halide, an alkaline material and at least about 5g./mole of silver halide of a 3-pyrazolidone selected from those havingthe formulas:

ing from 1 to 12 carbon atoms, and an aryl group; and

R represents a group selected from the class consisting of an alkylgroup having from 1 to 12 carbon atoms and an aryl group; and anauxiliary developing agent selected from the class consisting of apolyhydric phenol and an ascorbic acid developing agent and when none ofsaid auxiliary developing agent is present, at least about 15 g./mole ofsilver halide of said 3-pyrazolid0ne silver halide developing agent,said element containing a small amount of moisture that is suflicient todevelop a latent image in said silver halide to a stable silver imageupon heating to a temperature above about 50 C., the silver halide insaid emulsion layer having grains with an average diameter of less thanapproximately 1.5 microns, the silver halide being predominately silverbro- -mide, and the said silver halide emulsion being such that whencoated without the alkali and without the developing agent atapproximately 1500 square feet per mole of silver halide on a papersupport and exposed through a step wedge varying in density from 4.0 to0.3 to a high intensity light source and then processed in a developerof the following composition:

, Grams 1-phenyl-3 -pyrazolidone 5.0 Sodium sulfite 6 0 Sodiummetaborate :0

Ascorbic acid 27.0 Potassium bromide 2.0 Sodium thiosulfate,pentahydrate 2.0

Water to make 2.0 liters.

for 16 minutes at 20 C. gives a minimum reflex density less than 0.35and a maximum density of at least 0.20 greater than the minimum density.

29. A light-sensitive, unexposed photographic element of claim 28 inwhich the support is paper.

30. A photographic process which comprises applying a sufiicient amountof heat to a photographic element containing a small amount of moistureincluding a silver halide emulsion layer containing a latent image,integral and contiguous thereto an alkaline material and at least aboutg. per mole of silver halide of a 3-pyrozolidone silver halidedeveloping agent, to develop a silver image in the emulsion layer thesaid small amount of moisture being sufiicient to develop a latent imagein said silver halide to a silver image upon heating to a temperatureabove about 50 C.

31.- A photographic process which comprises exposing to a subject aphotographic element including a silver halide emulsion layer,contiguous alkaline material, a saccharide, and at least about 5 g. permole of silver halide of a 3-pyrazolidone silver halide developingagent, and applying a sufficient amount of heat to said exposed elementcontaining a small amount of moisture to develop a silver image in theemulsion layer the said small amount of moisture being suflicient todevelop a latent image in said silverhalide to a silver image uponheating toa temperature above about 50 C.

32. A photographic process which comprises exposing to a subject aphotographic element including a silver halide emulsion layer,contiguous alkaline material, nonreducing oligosaccharide, and at leastabout 5 g. per mole of silver halide of a 3-pyrazolidone silver halidedeveloping agent, and applying a sufiicient amount of heat to saidexposed element containing a small amount of moisture to develop asilver image in the emulsion layer the said small amount of moisturebeing suflicient to develop a latent image in said silver halide to asilver image upon heating to a temperature above about 50 C.

33. A photographic process which comprises exposing to a subject aphotographic element including a silver halide emulsion layer,contiguous alkaline material, nonreducing oligosaccharide, and at leastabout 5 g. per mole of silver halide of 1-phenyl-3-pyrazolidone, andapplying a suflicient amount of heat to said exposed element containinga small amount of moisture to develop a silver image in the emulsionlayer the said small amount of moisture being suificient to develop alatent image in said silver halide to a silver image upon heating to atemperature above about 50 C.

34. A photographic process which comprises exposing to a subject aphotographic element including a silver halide emulsion layer,contiguous alkaline material, at least about 15 g. per mole of silverhalide of a silver halide developing agent of the class consisting ofpolyhydric phenol and ascorbic acid developing agents, and at leastabout 5 g. per mole of silver halide of a 3-py-razolidone silver halidedeveloping agent, and applying a sufiicient amount of heat to saidexposed element containing a small amount of moisture to develop asilver image in the emulsion layer the said small amount of moisturebeing suflicient to develop a latent image in said silver halide to asilver image upon heating to a temperature above about 50 C. 35. Aphotographic process which comprises exposing to a subject aphotographic element including a silver halide emulsion layer,contiguous alkaline material, a saccharide, at least about 30 g. permole of silver halide of an ascorbic acid, and at least about 5 g. permole of silver halide of a 3-pyrazolidone silver halide developingagent, and applying a sufiicient amount of heat to said exposed elementcontaining a small amount or moisture to develop a silver image in-theemulsion layer the said small amount of moisture being sufiicient todevelop a latentimage in said silver halide to a silver image uponheating to a temperature above about 50 C.

36. A photographic process which comprises exposing to a subject aphotographic element including a silver halide emulsion layer,contiguous alkaline material, a nonreducing oligosaccharide, at leastabout 30 g. per mole of silver halide of an ascorbic acid, and at leastabout 5 g. per mole of silver halide of a 3-pyrazolidone silver halidedeveloping agent, and applying a sufiicient amount of heat to saidexposed element containing a small amount of moisture to develop asilver image in the emulsion layer the said small amount of moisturebeing sufficient to develop a latent image in said silver halide to asilver image upon heating to a temperature above about 50 C.

37. A photographic process which comprises exposing to a subject aphotographic element including a silver halide emulsion layer,contiguous alkaline material, sucrose, at least about 30 g. per mole ofsilver halide of an ascorbic acid, and at least about 5 g. per mole ofsilver halide of 1-phenyl-3-pyrazolidone, and applying a sufiicientamount of heat to said exposed element containing a small amount ofmoisture to develop a silver image in the emulsion layer the said smallamount of moisture being sufficient to develop a latent image in saidsilver halide to a silver image upon heating to a temperature aboveabout 50 C.

38. A photographic process which comprises exposing to a subject aphotographic element including a silver halide emulsion layer,contiguous alkaline material, a

saccharide, at least about 15 g. per mole of silver halide of apolyhydric phenol silver halide developing agent, and at least about 5g. per mole of silver halide of a 3- pyrazo-lidone silver halidedeveloping agent, and applying a sufi'lcient amount of heat to saidexposed element containing a small amount of moisture to develop asilver image in the emulsion layer the said small amount of moisturebeing sufficient to develop a latent image in said silver halide to asilver image upon heating to a temperature above about 5 0 C.

39. A photographic process which comprising exposing to a subject aphotographic element including a silver halide emulsion layer,contiguous alkaline material, a non-reducing oligosaccharide, at leastabout 15 g. per mole of silver halide of a polyhydric phenol silverhalide developing agent, and at least about 5 g. per mole of silverhalide of a 3-pyrazoliclone silver halide developing agent, and applyinga suflicient amount of heat to said exposed element containing a smallamount of moisture to develop a silver image in the emulsion layer thesaid small amount of moisture being sufiicient to develop a latent imagein said silver halide to a silver image upon heating to a temperatureabove about 50 C.

40. A photographic process which comprises exposing to a subject aphotographic element including a silver halide emulsion layer,contiguous alkaline material, sucrose, at least about 15 g. per mole ofsilver halide of hydroquinone, and at least about 5 g. per mole ofsilver halide of 1-phenyl-3-pyrazolidone, and applying a sufficientamount of heat to said exposed element containing a small amount ofmoisture to develop a silver image in the emulsion layer the said smallamount of moisture being sufiicient to develop a latent image in saidsilver halide to a silver image upon heating to a temperature aboveabout 50 C.

41. The process of claim 30 wherein the application of heat is effectedby passing the element over a heated roller.

42. A photographic process which comprises exposing a light-sensitivephotographic element containing a small amount of moisture, said elementcomprising a support having thereon a sulfur and gold sensitized silverhalide emulsion and integral and contiguous to the silver halide atleast about 5 g. per mole of silver halide of a 3-pyrazolidone silverhalide developing agent, and an alkaline compound, said small amount ofmoisture being sufficient to develop a latent image in said silverhalide to a silver image upon heating to a temperature above about 50C., and heat developing the exposed emulsion.

43. The process of claim 42 wherein the developing agent is a member ofthe class consisting of l-phenyl-4- 25 methyl-3-pyrazolidone,1-phenyl-4,4-dimethyl-3-pyrazolidone, 1 phenyl 2 acetyl 3 -pyrazo1id0ne,3 acetoxy 1 phenyl 2 pyrazoline, the enOl acetate of lphenyl 3pyrazo-lidone, 3 acetoXy 4 methyl 1- phenyl-2-pyrazoline and the enolacetate of 4-methy1-1- pheny1-3-pyraz0lidone.

References Cited by the Examiner UNITED STATES PATENTS 2,592,368 4/1952Yackel 96-95 2,624,674 1/ 1953 Tarkington et a1 96-108 2,751,300 6/1956James et al. 96-66 2,855,299 10/1958 Rogers 9629 3,022,168 2/1962Stjarnkvist 96-66 26 3,062,648 11/1962 Crawford 9676 3,088,824 5/1963Jacobs 96-63 3,248,219 4/1966 Jacobs 96--66 OTHER REFERENCES Weyde, E.abstract of Belgian Patent No. 586,348 (1- 1959). Published in AnscoAbstract 1444 Ha.

Gareis, et al., abstract of Belgian Patent No. 599,383 (1-1960).Published in Ansco Abstract 1412.1Ib. 10 Inagaki, K., abstract ofJapanese Patent No. 176,111.

Published in Chem. Abstr. 45, 4590 (6-1951).

NORMAN G. TORCHIN, Primary Examiner.

A. D. RICCI, C. E. DAVIS, Assistant Examiners.

@2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,31 2,550 Dated Paul H. Stewart, George E. Fallesin Inventm-(s) and JohnW. Reeves, Jr.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 22, lines 2? through 33, in the righthand structural formula,that portion reading SEALED DEZ2 1969 Amt:

Eanrdunetchml WILLIAM E. SGHUYLER, JR.

Attesting Officer Oomissioner of Patents L J

1. A LIGHT-SENSITIVE, UNEXPOSED PHOTOGRAPHIC ELEMENT COMPRISING ASUPPORT HAVING THEREON A SILVER HALIDE EMULSION LAYER AND CONTAGIOUS TOTHE SAID SILVER HALIDE, AN ALKALINE MATERIAL AND AT LEAST ABOUT 5G./MOLE OF SILVER HALIDE OF A 3-PYRAZOLIDONE SELECTED FROM THOSE HAVINGTHE FORMULAS: